ELSEVIER Physica B 211 (1995)423-429 Resonant magnetotunneling via quantum confined states P.H. Beton*, J. Wang 1, N. Mori z, L. Eaves, H. Buhmann, L. Mansouri, P.C. Main, T.J. Foster, M. Henini Department of Physics, Universityof Nottingham, Nottingham NG7 2RD, UK Abstract We have measured the low temperature current voltage characteristics (I(V)) of GaAs/AIAs resonant i tunnelling diodes with sub-micron lateral dimensions. Additional peaks in I(V) are observed due to resonant turlnelling via one-dimensional quantum wire states. In the presence of a magnetic field oriented perpendicular to the ~urrent and parallel to the wire the peaks show a complex splitting evolving into a regular series at high field with up to 20 resonances. For the smallest device we are able to deduce the probability density of the lowest three bound states from tile magnetic field dependence of the current and show that the confining potential is close to parabolic. For a magnetic fi~ld which is perpendicular to both the current and the wire a much weaker dependence on magnetic field is observed cor~firming the one-dimensional nature of our device. Finally, in the presence of a field oriented parallel to the current a ~ontinuous transition from electrostatic (at low field) to magnetic confinement (at high field) is observed. Resonant tunnelling diodes display pronounced non- linearities in their I(V) characteristics which are a direct consequence of the formation of quasi-bound states within the quantum well which forms their active region [1]. The quantum well is formed between two tunnel barriers and in a large area diode electrons are free to move parallel to the well and barriers, i.e. there is transla- tional symmetry in this plane. Over the last few years several groups have investigated the I(V) characteristics of small area diodes [2-7] in which additional peaks are observed in I(V) due to the breaking of translational symmetry. This can be caused by one of two possible mechanisms. The first is that fluctuations associated with *Corresponding author. 1 Present address: Department of Physics, HKUST, Clear Water Bay, Kowloon, Hong Kong. 2permanent address: Department of Electronic Engineering, Osaka University, Osaka, Japan. inhomogeneities (for example the presence i of donors within the quantum well) which give rise to a ~tatistically averaged background current in a large area[ diode may be resolved as sharp peaks for a small area[ diode [7]. This is a mesoscopic effect [8]. The second iis that the small dimensions of the device may cause fuither quan- tisation of the motion of electrons parallel to ~he barriers, and that resonant tunnelling via these latera!ly confined states gives rise to additional peaks in I(V). It [was argued that this was the origin for the additional peaks observed in the first work on such devices [2]. Ho~vever it is clear that the distinction between these two possible mechanisms for a particular device is extremely diffi- cult, and we have argued that some previous ~vork which was attributed to lateral quantisation is actt~ally due to inhomogeneities [9]. In this paper we will! show that a magnetic field may be used to unambiguqusly distin- guish the effects of lateral quantisation arm inhomo- geneities. The devices we use for this work are fabricated from an AIAs/GaAs heterostructure. The GaAs quantum well 0921-4526/95/$09.50 ~, 1995 Elsevier Science B.V. All rights reserved SSDI 0921-4526(94)01084-6